JP 2001-173476 A describes an idle reduction technology as a countermeasure against exhaust emissions or for improvement of fuel efficiency, which stops an engine automatically when a vehicle stops and the engine is an idling state, and restarts the engine when the vehicle starts moving.
A steering-by-wire system consumes electric power in turning wheels with a turning motor and in generating a steering reaction force with a reaction force motor. However, an alternator is stopped in an idle reduction state such as the above-mentioned prior art, and thus available electric power for an ordinary engine vehicle other than a hybrid vehicle is limited. Therefore, when the steering-by-wire is performed ordinarily in the idle reduction state, the voltage of the battery may drop, and the other electric system may be affected.